- Fail Error on FBX Export, Cannot Export Model
Just a guess here:
I suspect this was based on something like the cube mesh, which comes with its own UVs even if you don't do anything with them, and that is what's causing this. Or maybe you built that side from scratch so it really doesn't have any UVs but everything else does, and FBX export is looking for a UV even though it won't end up being used.